Cordless telephones include a base unit, which is typically in a relatively “fixed” location, and a handset, which may be cradled in the base unit, such as when charging a battery, or which may roam relative to the base unit, such as when engaged in a telephone call. The base unit is typically coupled to a network, such as the Public Switched Telephone Network (PSTN), via a physical connection. The base unit is also coupled, via an RF connection, to the handset. Thus, when a user is engaged in a telephone call, the user interacts with a microphone and a speaker in the handset, associated RF signals are transmitted between the handset and the base unit, and the base unit interfaces with the network.
Some conventional cordless telephones take advantage of the RF link between the base unit and the handset by enabling an intercom mode. In this mode, for example, a user who is at a location remote from the base unit may use the intercom mode to communicate with another user located near the base unit. The particular methods of establishing the intercom vary amongst the conventional cordless telephones.
For example, some conventional telephones allow the user with the handset to initiate an intercom mode connection by activating a key on a keypad of the handset, thereby causing a signal to be transmitted over the RF link to the base unit. This signal may automatically initiate the intercom mode. Alternatively, the intercom mode may begin when the other user at the base unit responds to an alert, such as an audible signal, by activating a key on the base unit. Alternative cordless telephone configurations enable a user to initiate an intercom mode from the base unit, such as during a paging operation. Of course, some cordless telephones enable the intercom mode to be initiated from either the base unit or the handset.
Regardless of the initiation method, one consistent prerequisite to the intercom mode is that the cordless telephone must be in an on-hook condition (i.e., there is not an on-going telephone call) prior to the initiation of the intercom mode. This requirement is mandated by the fact that there is only one RF link between the base unit and the handset, and that if the link is employed in an on-going telephone conversation, then it cannot be employed for intercom purposes.
Another conventional feature mandated by the existence of a single link is that an on-going intercom conversation cannot be maintained in the presence of a new incoming call. Conventionally, therefore, when a new call is incoming, the cordless telephone terminates the intercom mode prior to causing a ringing signal to be produced by the base unit and/or the handset. This can be inconvenient in that it may abruptly terminate an on-going discussion of import. This inconvenience may be especially pronounced if the incoming call is of little or no import, such as a telemarketing solicitation. There is therefore a need for a more intelligent way of handling an incoming call in a cordless telephone engaged in an intercom mode.